Pot dial Idea - Adjusting Power on Demand

Tagg · Jun 28, 2010

I had a really awesome idea, not sure if this has been done before or if anyone thought of this. What if you could connect the internal pot to an external dial to adjust the power on demand? Is this possible? If so, is this a practical idea?

-Zachary

Seoul_lasers · Jun 29, 2010

Tagg said:
I had a really awesome idea, not sure if this has been done before or if anyone thought of this. What if you could connect the internal pot to an external dial to adjust the power on demand? Is this possible? If so, is this a practical idea?

-Zachary

Yes, most of the drivers featured here have pots to adjust current to the diode.
However it is NOT a good idea to change the pot during firing or you'll end up with a spike that'll end your diode's life.

An external pot has been done on labbys before. Nothing new here.

Tagg · Jun 29, 2010

Ah, I see. Well, that just shows how inexperienced I am in the world of lasers...learning fast though!

lasersbee · Jun 29, 2010

That subject has been discussed on the Forum in the Past..
It did not come to fruition... yet....

Jerry

Grix · Jun 29, 2010

3zuli · Jun 29, 2010

this would be possible, but the driver must have some current limitation (like 30-110mA for PHR) and must be very stable output to prevent diode damage
or you could use PWM modulation and TTL driver

wolfram · Jun 29, 2010

I dont know what pots are being smoked here, but i think its time for someone to create a digital pot for micro drivers . laserbee you the man with the digital experience.

Asherz · Jun 29, 2010

wolfram said:
I dont know what pots are being smoked here, but i think its time for someone to create a digital pot for micro drivers . laserbee you the man with the digital experience.

You do realise drivers are smaller than the tip of your finger? There's just no room.

Tech_Junkie · Jun 29, 2010

I think DieselMarine did this. He added a pot between the driver and the LD.

3zuli · Jun 29, 2010

Tech_Junkie said:
I think DieselMarine did this. He added a pot between the driver and the LD.

this could work, but at higher currents there's big risc of damaging (= burning) the pot

[let's think about ddl driver - it's the simplest] better way to do this would be using 100 or 50ohm pot with 12.5ohm resistor in series so the pot can change the current from about 20mA to 110mA
it also might be good to add an capacitor (like 10uF/16V) in series with the pot to prevent current spikes (is that right? :thinking

but I'd rather use PWM modulation

this is what I mean

Lumify · Jun 30, 2010

I brought this idea up about a month ago, and we came up with a bunch of ideas here. I never actually went through with it though. The 445nm craze swept through the forum and I forgot about the whole thing. :friend: I'd be very interested to see someone actually pull off something like this and tell us how they did it.

edit:Check out post #32 in that thread. That was the approach I was thinking of using.

Benm · Jun 30, 2010

It is very simple to make in terms of electronics. I suppose the limiting factor is mostly mechanical, with many hosts simply lacking space to fit a potentiometer that adjusts the current.

With these lm317 based drivers, there is also the problem of a fair amount of power dissipation in the pot, but that could very easily be remedied by using better driver designs.

I think the reason why its rarely done is simply a lack of demand: most people want their lasers running at maximum permissble current all the time. If you have any need for power control and the space to fit a pot inside your host, just go for it though!

Tech_Junkie · Jun 30, 2010

Just went through DMs threads. His flashlight had a dimming feature, and was hooked up to the battery, not the diode.

Pot dial Idea - Adjusting Power on Demand

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